Static digital images can readily be obtained, for example, using a digital camera or a scanner. Other static images may be computer-generated or downloaded from pre-existing image databases. Static digital images may be displayed using a digital display device such as a computer monitor, digital projector, or the like, and are typically shown either individually or as part of a computerized “slide-show” presentation (e.g. using Microsoft™ PowerPoint™).
However, with static images, often it is only possible to retain the viewer's interest and attention for a very limited period of time. Moving video is often considered to be more effective at holding the viewer's attention.
With conventional (i.e. non-digital) static images, the television and film industries developed rostrum camera techniques to enable moving video to be generated from static images such as photographs or paintings, thereby enhancing the viewer's interest in the image. Rostrum camera techniques are well established, and typically involve moving the camera relative to the static image to give a panning effect, zooming the camera in to features of interest, and zooming out to reveal a wider field of view.
Generating moving video from a static digital image using virtual rostrum camera techniques is also possible. These techniques enable the viewer to be taken on a visual tour around regions of interest in the image. WO 00/08853 describes an example of such a technique, in which the user manually specifies the positions of key frames over the image, and then the computer automatically generates a path of panning between the key frames at a fixed rate. Alternatively, the user can manually generate the path of panning between the key frames at a controlled rate.
A related example of a technique for generating video from a static digital image is given in WO 97/31482. Here, the user of a spherical image file can specify panning movements over the image to generate a default video tour of the image, or can interrupt the tour to specify his own angle of view and travel using on-screen control icons.
The panning of a virtual rostrum camera across a static digital image can be automated by computer, as described in GB 2372658 A. Here, an image processing system is employed to locate regions of visual interest (e.g. people's faces) in the image and to generate an automated rostrum camera movement between them. The image processing system designates a region as being of visual interest if its visual characteristics satisfy predetermined rules. The regions of interest so extracted then become route destinations in the video tour of the image, which is further constrained by pre-determined aesthetic rules governing the sequence of panning and zooming, and preset times for dwelling on the regions and for covering each image if a set of images is used.
Neither the manual nor automated methods are entirely satisfactory from the user's point of view. Manual methods for specifying panning and zooming operations are time-consuming and are likely to be too complex for consumer applications where they might have most benefit. Automatic methods, on the other hand, only find regions of visual interest in an image which satisfy the predetermined rules, and these may not correspond to regions of psychological interest, such as those features which would be noteworthy in a story about the image.
Accordingly, there is a need for a method for generating video from a static image which is intuitive and easy to use, and which enables the video content to correspond to the features that would be pointed out by someone verbally telling a story about the image or explaining the features therein.